It seems like one reason why Russia’s actions in Crimea appear so jarring and brazen is that it’s a form of warfare that was once common but rarely take place anymore. Russia may not formally annex Crimea – it seems more likely that the territory will declare independence under heavy Russian influence – but it has essentially invaded another country to lob off a piece of territory that was, despite longstanding nationalist sentiment, an undisputed part of Ukraine.

Stunned by Russia's swift move into the autonomous province of Crimea and the Russian parliament's endorsement of that brazen action, the United States called on Moscow to withdraw its forces from the region and "refrain from any interference elsewhere in Ukraine." Speaking by phone with Russian President Vladimir Putin for the first time since this crisis escalated, President Obama expressed concern over "Russia's clear violation of Ukrainian sovereignty and territorial integrity," according to a White House statement.